Microphone and circuit



May'31', 1-938. H. F. OLSON ET AL ,3

MICROPHONE AND CIRCUIT Filed May 25, 1955 INVENTORS HARRY F. OLSON BY BARTON KREUZER ATTORNEY Patented May 31, 1938 Barton Kreuur, Rockaway Park, N. Y., ass! or! to Radio Corporation of America, a corporation of Delaware Application May 25, 1935, Serial No. 23,460

2 Claims.

The present invention relates generally to microphone systems and more particularly to. microphone systems in which means are provided for mixing the outputs of a plurality of individual microphones.

able to have a plurality of microphones located at different points and connected with a central transmission line so that the output of one or more of the microphones can be supplied to connect or disconnect one microphone instantaneously: The better practice is to slowly mix the output from one microphone with the output of another, or to slowly fade out the output of a trol of the individual microphones 30a, 30b and 300 is obtained by varying the energy supplied to the field winding, of the microphones which are of the electro 'vnamic type. Each of the microphones 30a, 30.), 300 is provided with a diaphragm 3| to which is secured a moving coil 32 having leads 33. The leads 33 are connected through transformers 34 having series connected secondaries, to the primary of an audio frequency transformer 35. Transformer 35 couples the microphone system to a suitable amplifier 36. The various moving coils 32 are vibrated in their respective magnetic fields set up by windings 31a, 31b, 310. The control system is obtained by varying the energy supplied to these windings.

The energy. for the windings 31a, 31b, 310 is obtained from a suitable source which is preferably shunted by a resistor 38. A second resistor 39 is connected in shunt with either the entire resistor 38 with a part thereof, by means of a variable tap 40. The field windings 31a, 31b, 310 are energized from resistor 39 by suitable leads in conjunction with variable taps Ma, Mb, 0, each of which is adjustable over the entire length of the resistor. With this arrangement the amount of energy for energizing each of the windings 31a, 31b, and 37c can be independently varied from zero to the maximum value available.

, Thus, each microphone can Zoe cut in or faded out as desired.

It will be apparent, from the foregoing specification, that by the term moving co as used in the specification and appended claims, we are In the reproduction of sound it is often desirnot limited to a circular winding composed of a multiplicity of turns, but that we may use a winding of any shape or number of turns, such, for example, as the single straight conductor used in the type of device known as ribbon or velocity microphones, or a single straight wire connected to a diaphragm, as in some types of inductor microphones.- All of these types of microphones have the property in common of having a conductor vibrated in a magnetic held.

The modification illustrated and described in the foregoing specification is to be considered exemplary; only, and various other modifications and changes may be made without departing from the spirit of the invention. It is, therefore," to 'be understood that the invention is to be limited only by the scope of the appended claims.

We claim:

1. A system for cutting in and fading out one or more microphones comprising a plurality of microphones each including a moving coil, leads for combining the outputs of said moving coils, a field coil in each microphone for energizing the microphone, and means for independently varying the outputs from said moving coils at will, the said means includingconnections for selectively controlling the amount of energy supplied to each of said field coils.

2. A system for cutting in and fading out microphones comprising a plurality of microphones each including a moving coil, leads for combining the outputs of said moving coils, a magnetic field in each of said microphones for converting sound waves into electrical variations, a winding in each microphone for producing said fields, a single source of energy and leads from said single source of energy to said field windings for supplying energy from said source to said windings, and means for independently varying the outputs from said moving coils at will, the said means including connections for selectively controlling the amount of energy supplied to each of said field windings from said source.

HARRY FERDINAND oLsoN. BARTON. xanuzna. 

